1. Field of the Invention
The invention relates to a device for filling and sealing sacks, which are open on one side and are provided preferably with side folds.
2. Description of the Related Art
Such a device is disclosed, for example, in the EP 290 879 A2 and DE 93 01 355 U. The device described therein exhibits a filling station, which exhibits a filling pipe and serves the purpose of filling sacks preferably with granules or dust-like filling material. The device exhibits various grippers for transporting the empty sacks, holding the sacks in the filling station and for transporting away the filled sacks in the device. Below the filling station is a conveyor belt for bracing and for carrying away the filled sacks from the filling station. This conveyor belt exhibits at least one stand that revolves around two deflecting rollers. In the prior art devices the bottom welds are affixed to the thermoplastic tube, which is hauled off a supply roller, in a region before the filling station. If at this point the device is driven at a high cycle rate, the bottom weld has not cooled and thus has not reached its final hardness at the time the sack is delivered to the filling station and filled there. If then the sack is suddenly filled by means of the filling funnel, thus putting a sudden stress on the bottom weld, the sack can split. The result is that the machine has to be shut down.
A device for filling sacks is also discloses in the EP 468 376 B2. In this device a conveyor belt is arranged below the filler. A part of the conveyor belt can be swung away. On this part rests the empty sack with the bottom end turned up so that the seam is not excessively stressed at the first filling shot. As the filling procedure continues, the part of the belt that is under the sack swings away downwardly so that the bottom can form. Once this has happened, this part of the belt continues to swing up and down rhythmically in order to compress the fill material. The drawback with this procedure is that when thin walled sack material is used, the material in the area of the top holding pliers is stressed to the point that it stretches so that the sack can be damaged. Another drawback with this device lies in the fact that relatively large masses have to be moved in the vibrating and compressing process.
The object of the invention is to provide a device of this class, that guarantees both a flawless bottom formation during the filling process and secondly flawless compression without having to move large masses.
The invention solves this problem associated with this class of device. In this respect the conveyor belt in the region below the filling station can be lowered and raised again by swivelling the deflecting roller. Below the carrying run of the conveyor belt there is an additional vibrator in the region of the filling station. This design of the conveyor belt allows the sack, held in the filling station, to be safely filled. Then the unfilled sack with the bottom weld, which has not yet completely cooled, is hung in the filling station, where the grippers of the filling station grasp the sack at its open end. The closed end of the sack lies on the carrying run of the conveyor belt. Said carrying run is arranged below the filling station. The distance from the filling station to the carrying run of the conveyor belt is less than the length of the unfilled sack. Therefore, the bottom end of the yet unfilled sack lies bent over on the carrying run of the conveyor belt. As the sack is being filled, the sudden impact of the filling procedure is attenuated in that the fill strikes the floor of the conveyor belt and does not suddenly stress the weld region in the bottom seam that has not completely cured yet. Following this damped prefilling, there is the problem of the sack forming a good bottom. For this purpose the deflecting roller, mounted on this end of the conveyor belt, is lowered. To compress the fill material, the conveyor belt is set vibrating by means of the vibrator, mounted below the carrying run in the filling station area, for the purpose of giving the sack bottom suitable jolts in order to compress the fill material.
Advantageous embodiments of the invention follow from the dependent claims that refer back to the main claim.
Correspondingly the deflecting roller can be swivelled by means of a pneumatically or hydraulically driven lever bar.
Whereas the deflecting roller of the conveyor belt can be raised and lowered periodically, the sack bottom can be vibrated at a low frequency during the filling process, as described above.
Posts that run crossways can be mounted on the conveyor belt. The distance between the posts can be selected in such a manner that they can accommodate a filled sack between any two posts. If such transverse posts are present, there is the problem that the empty sack segments arriving by means of a pair of transport gripper may strike, during delivery in the filling station, i.e. to the grippers of the filling station, with their freely hanging ends against the posts; and consequently the free end is not correctly deposited on the conveyor belt between the posts. Therefore, the invention solves this problem by arranging a bar, which runs at right angle to the direction of transport, in front of and above the conveyor belt in the opposite conveying direction of the sacks, conveyed into the filling station by the grippers. The sacks can be pulled over the bar in such a manner that the sacks are deposited by means of a specific swivel motion with the sack bottom between two posts of the conveyor belt.
The entire conveyor belt can be vertically adjusted in the machine frame. Thus, it is easy to adapt to the different sack sizes.